Answer
$e^{nx}$
Work Step by Step
$(coshx+sinhx)^{n}$ = cosh nx + sinh nx
Convert the left side to the $e^{x}$ forms and simplify
$(\frac{e^{x} + e^{-x}}{2} + \frac{e^{x} - e^{-x}}{2} )^{n}$ = $(\frac{2e^{x}}{2})^{n}$
= $(e^{x})^{n}$ = $e^{nx}$